A conventional valve timing control apparatus of this type is disclosed in Patent Document 1 below.
The apparatus of the Patent Document 1 referenced below is adapted to advance the phase angle of the camshaft relative to the drive plate 2 (sprocket) driven by the crankshaft of an internal combustion engine in the rotational direction of the drive plate 2 (the direction for advancing the phase will be hereinafter referred to as “phase-lead direction” or phase-lead angle side”), or to delay the phase angle in the opposite direction (the direction will be hereinafter referred to as “phase-lag direction” or phase-lag angle side”), to thereby change the opening/closing timing of valves driven by the cams of the engine.
In the apparatus of Patent Document 1, the drive plate 2 (sprocket) is rotatably mounted on the spacer 8 integral with the camshaft 1. Fixedly secured ahead of the spacer 8, and mounted together with the spacer 8 to the camshaft 1 with a bolt 18, is a lever shaft 13 having three radially extending levers 12. A link arm 14 is rotatably linked at one end thereof to the lever 12 by means of a coupling pin 16, and a movable manipulation member 11 is rotatably mounted to the other end of the arm 14 by means of a coupling pin 17. The drive plate 2 is provided with a radial guide 10 consisting of a pair of parallel guide walls 9a and 9b each extending in the radial direction. The movable manipulation member 11 is slidably mounted between the guide walls 9a and 9b. A ball-shaped rotatable member 22 is rollably accommodated in the semi-spherical recess 21 formed in the front end of the movable manipulation member 11.
On the other hand, a guide plate 24 is rotatably supported on the front end of the lever shaft 13 via a bearing 23. The guide plate 24 is provided on the rear face thereof with a spiral groove (spiral guide) 28 with its radius continually decreasing in the rotational direction of the drive plate 2. The ball 22 held in position by the movable manipulation member 11 engages the spiral guide 28.
As the guide plate 24 in engagement with the ball 22 is rotated under an external force in the phase-lag direction (i.e. in the direction opposite to the rotational direction of the drive plate 2) relative to the drive plate 2, the movable manipulation member 11 is moved along the radial guide 10 and spiral groove 28, thereby shifting radially inwardly. In response to this radially inward movement of the movable manipulation member 11, the camshaft 1 is rotated (that is, advance in phase) by the link action of the link arm 14 coupled to the lever 12 in the phase-lead direction relative to the drive plate 2, since the camshaft 1 is integral with the lever shaft 13, so that camshaft 1 is advanced in the phase relative to the drive plate 2.
On the other hand, contrary to the relative rotation in the phase-lag direction mentioned above, if the guide plate 24 is rotated in the phase-lead direction (rotational direction of the drive plate 2) relative to the drive plate 2 by a torque transmitted from the engaging balls 22, the movable manipulation member 11 is moved by the spiral groove 28 in the radially outward direction. As the movable manipulation member 11 is moved in the radially outward direction, the camshaft 1 is rotated in the phase-lag direction relative to the drive plate 2, so that camshaft 1 is retarded in phase relative to the drive plate 2.
That is, in the apparatus of Patent Document 1, the phase angle of the camshaft 1 is advance or retarded in phase relative to the drive plate 2 by applying a torque to the guide plate 24 so as to rotate the guide plate 24 in the phase-lead or phase-lag direction relative to the drive plate 2. This torque for causing the relative rotation of the guide plate 24 against the drive plate 2 is applied using a planet gear mechanism 25 coupled to a first and a second electromagnetic brake (26, 27), as shown below.
This planetary gear mechanism 25 comprises: a sun gear 30 integral with a braking flange 34 that is rotatably coupled to the front end of the lever shaft 13 via a bearing 29; a ring gear 31 formed on the inner surface of the recess formed at the front end of the guide plate 24; a carrier plate 32 securely fixed between the bearings 23 and 32 and to the lever shaft 13; and a plurality of planetary gears 33 rotatably supported by the carrier plate 32 to engage sun gears 30 and 31. The first and second electromagnetic brakes 26 and 27 are arranged to face the front ends of the guide plate 24 and braking flange 34, to thereby hinder the rotations of the guide plate 24 and flange 34.
Hence, the guide plate 24 is acted upon by a braking torque of the electromagnetic brake 26, and is rotated in the phase-lag direction relative to the drive plate 2. On the other hand, the sun gear 30 is acted upon by a braking torque of the electromagnetic brake 27, and is rotated in the phase-lag direction relative to the carrier plate 32. In this case, the ring gear 31 is accelerated by the spinning of the planetary gear 33. Consequently, as the sun gear 30 is braked by the electromagnetic brake 27, the guide plate 24 is acted upon by a torque that causes the guide plate 24 to rotate in the phase-lead direction relative to the drive plate 2. Thus, the phase angle of the camshaft 1 relative to the drive plate 2 is varied in either the phase-lead direction or phase-lag direction in accordance with the torque applied to the guide plate 24.
On the other hand, the valve timing regulation apparatus of Patent Document 2 has a rotational member 12 that is rotatably supported by an output shaft 22 integral with the camshaft 4 and is driven by the crankshaft. An electric motor 70 is provided to rotate the eccentric shaft 18 integral with an action shaft 72. The rotation of the eccentric shaft 18 in turn rotates an output shaft 22 via a ring gear 14 and a planetary gear 30 that rotates in the direction opposite to that of the eccentric shaft 18. Thus, by rotating the camshaft 4 relative to the rotational member 12 supported by the output shaft 22, the phase angle between them is changed to vary the valve timing.    Patent Document 1: Japanese Patent Application Laid Open 2006-77779.    Patent Document 2: Japanese Patent Application Laid Open 2004-3419.